I had a Scott American Bulldog who loved the water, but she would sink like a rock. I got her a life jacket so she could "swim" a bit more easily. Michael Phelps, she was not, but watching her paddle towards the shore made my heart melt! Bullies are amazing.
Had a few Bull terriers over the years, though very heavy for their size, I never would expect one to sink. I bet she loved it once you found a way around it